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Old 19th November 2003, 04:39 PM   #1
pete.a is offline pete.a  United Kingdom
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Question Diy Phono stage

Hi,

Doe's anyone know of a phono stage using 6922/ecc88. Im pouring over Bruce Rosenblit'z book at present, but it looks a bit too much to build. Not so sure about all that voltage rattling around ! And don't worry im an electrician by trade, so schematics would be usefull.
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Old 19th November 2003, 06:29 PM   #2
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here you can find a phono stage made with the 6DJ8-ECC88, the 6922 have some better performance but is the same tube

http://web.tiscali.it/audiofanatic3/...Valvolari.html

ciao
Filippo
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Old 19th November 2003, 10:21 PM   #3
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Default Re: Diy Phono stage

Quote:
Originally posted by pete.a
Doe's anyone know of a phono stage using 6922/ecc88.
I've built this one. It's definitely the best single ended phono amp I've ever heard, and by no small margin.
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Old 20th November 2003, 01:24 AM   #4
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Hi,

To me it still looks as a desperate attempt from an otherwise brilliant designer; it says to me: I wasn't able to solve that part so I resorted to a FET.

Good sounding as it may, it's still a failure to me.

And that's just my opinion.

Cheers,
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Old 20th November 2003, 04:30 AM   #5
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Quote:
Originally posted by fdegrove
To me it still looks as a desperate attempt from an otherwise brilliant designer; it says to me: I wasn't able to solve that part so I resorted to a FET.

Good sounding as it may, it's still a failure to me.
Bollocks. It's a brilliant design that uses the best of both to get lots of gain, low distortion and low noise in one stage. Still haven't ever seen a tube design with noise anywhere near the cascode's or a transformer with it's resolution. It's cheap (the FET) too.

Don't tell Allen, but subbing in an ECC99 for the second tube makes it even better.
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Old 20th November 2003, 09:06 AM   #6
AKSA is offline AKSA  Australia
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O Frank,

You are otherwise such a tolerant, friendly and clever beast, and here you go saying Alan has failed because he used a FET!!

I've been there....... with Mick Maloney's Supratek design (I had input on the power supply). I can tell you the FET pulls back noise by a huge margin - quite audible - even with selected tubes (Mick used 417A) the addition of the FET reduced noise by around 10dB. This is no small thing, particularly on a MC phono, and it was achieved with SS, one thing it's good at. And the tubes still add that indefinable something which makes the design instantly recognisable to the tubophile, I promise you.

My own GK-150 design is also a hybrid; SS front end, tube output stage. I even go so far as to use a quality IC for the phono stage. You won't believe how quiet and powerful sounding it is. There are a few things tubes can't do, at least not without huge complexity, completely overshadowing the object of the exercise!

Cheers,

Hugh
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Old 20th November 2003, 02:45 PM   #7
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Hi,

Quote:
You are otherwise such a tolerant, friendly and clever beast, and here you go saying Alan has failed because he used a FET!!
Not at all. I'm just saying I'd feel as if I'd failed...

Quote:
I've been there....... with Mick Maloney's Supratek design (I had input on the power supply).
I know, Hugh. I've seen the traces of that on the net at various places.

Quote:
Don't tell Allen, but subbing in an ECC99 for the second tube makes it even better.
I won't tell him... but it makes perfect sense to me. Well done, Brett.

Cheers,
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Old 28th November 2003, 12:47 AM   #8
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Allen's design is very nice, but if you want to try something different that has some good noise cancellation features, try this (schematic at bottom of page):

TubeCad Journal

I recommend that you read the entire article and also Part 1 (the previous month).

To get good PS noise cancellation C1=22n and C2=1u. If you change anything, these values will have to change. But, with these values you can get close to 60db noise reduction below the noise floor coming from the circuit and PS. If you build a good PS the total noise should be very much below the signal level.
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Old 28th November 2003, 01:38 AM   #9
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Hi,

Quote:
If you build a good PS the total noise should be very much below the signal level.
Yes, - 60dB from the PS in a phono stage is a starting point, -90dB is better still.

Every PS S/N should be well below the smallest imaginable signal or it's no good.

Your usual PITA,
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Old 28th November 2003, 02:13 AM   #10
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Yes, -90db is almost required. I did not say what I meant to say correctly.

Without the noise concellation circuit, the PS noise may already be considerably below the signal level, depending on the nature of the PS. Let's say it's 60db below for example.

The noise cancellation circuit in this design allows you to drop the noise floor more than 60db below that. So, hypothetically you'd get -120db. In practice this is hard to do, but the noise cancellation circuit will make whatever the raw design does a whole lot better.
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